streusel topping

I recently made Marian Bull's Blueberry Schlumpf. Delicious; love how simple and pure it is and how the blueberries really shine. The only change I made was to add a little lemon juice and lemon zest to the blueberries to help brighten their flavor. Anyway, it will now be a summer staple and probably equally good with other seasonal fruits. My question is the streusel topping. Is there a secret to keeping it firm and crunchy, like right out of the oven and cooled? Making it for a household of 1 or 2, it lasts for a few days, during which the streusel topping gets a bit soggy and slumps--not any less flavorful, but the textural difference is not as good, and the presentation would suffer, as well. On the counter, I just covered the pan with aluminum foil. Anyway, didn't know if there was a trick that I had missed along the way. Thank you.

I don't know of a "trick." For drier streusel a day or two later, you'd probably have to add so many more "dry" ingredients to the streusel (oats, flour, etc.) that the initial bake would be less tasty.

What if you left half the dish without topping on the first bake. Eat the first half, with topping, on the initial bake. Then add the remaining topping to the leftover half a day or two later. First heat in a low oven to warm through the fruit and cook the topping a little, then finish under the broiler for a few minutes to brown the topping.

Agree with Pegeen. Another way to achieve the crunch without overbaking...divide the fruit part into single serve containers and freeze. Divide the crunch part into single serve portions. Bake a serve or two as needed - fruit from freezer, crunch from pantry or fridge, where you store it.

You might try squeezing small handfuls of the streusel, instead of sprinkling it on top. You get crunchier nuggets of topping that way. And for storing, just wrap the pan in a clean tea towel and store it on the counter, or in a cupboard ( I put mine on top of the stack of dinner plates).